This invention relates to a system and a method for recovering potential energy of a hydrogen gas fuel supply in a vehicle and more particularly, to a system and method which uses an expander, compressor and a motor/generator to utilize the potential energy stored within hydrogen gas that is supplied to a fuel cell in order to provide pressurized air to the fuel cell and to generate electricity, thereby improving the efficiency and the fuel economy of the vehicle.
In order to reduce automotive emissions and the demand for fossil fuel, automotive vehicles have been designed that are powered by electrical devices such as fuel cells. These fuel cell-powered electric vehicles reduce emissions and the demand for conventional fossil fuels by eliminating the internal combustion engine (e.g., in completely electric vehicles) or by operating the engine at only its most efficient/preferred operating points (e.g., within hybrid electric vehicles).
Many fuel cells consume hydrogen gas and air (e.g., as a reaction constituent). The consumed hydrogen and air must be properly stored and transferred to the fuel cell at certain pressures in order to allow the fuel cell and vehicle to operate in an efficient manner.
Vehicles employing these types of fuel cells often include systems and/or assemblies for storing and transmitting hydrogen gas and air to the fuel cell. Particularly, the hydrogen gas is typically stored within a tank at a relatively high pressure and with a relatively high amount of potential energy. The hydrogen gas is then transferred to the fuel cell by use of several conduits and several pressure-reducing regulators which lower the pressure of the gas by a desirable amount. While the pressure of the hydrogen gas leaving the fuel tank is substantially lowered prior to entering the fuel cell, it is above normal atmospheric pressures which is required for efficient operation. The air that is communicated from the fuel cell is obtained at atmospheric pressures and must be pressurized or otherwise driven through the system in order to ensure proper and efficient fuel cell operation. This pressurization and/or driving of air through the system is typically performed by use of one or more compressors or turbines. These compressors or turbines require electrical energy for their operation, and therefore drain the vehicle""s battery and use generated electrical energy, which could otherwise be used to power the vehicle""s electrical components and accessories.
There is therefore a need for a new and improved system and method for use with a fuel cell powered vehicle which recovers the potential energy stored within pressurized hydrogen gas and which converts that potential energy to mechanical and electrical energy that can be used to drive a compressor, to supplement the electrical power demands of the vehicle and/or to recharge an electrical storage device.
A first non-limiting advantage of the invention is that it provides a system and method for recovering the potential energy of the compressed gas stored within a fuel cell-powered vehicle.
A second non-limiting advantage of the invention is that it provides a system and method for recovering the potential energy of the hydrogen gas stored within a fuel cell powered vehicle and which selectively converts the potential energy into mechanical and electrical energy which is selectively used to drive a compressor, supplement the electrical power demands of the vehicle, and/or to recharge an electrical storage device.
According to a first aspect of the present invention, a system is provided for recovering potential energy from a hydrogen gas fuel supply that is used to power a fuel cell within a vehicle. The system includes a fuel tank which stores pressurized gas; a first conduit system which selectively and fluidly couples the fuel tank to the fuel cell, effective to allow the pressurized gas to be selectively communicated to the fuel cell; an expander including a turbine which is disposed within the first conduit system and which is selectively and rotatably driven by the pressurized gas, effective to generate torque and lower the pressure of the pressurized gas which is communicated to the fuel cell; a second conduit system which selectively and fluidly couples the fuel cell to a source of air, effective to allow the air to be selectively communicated to the fuel cell; a compressor which is disposed within the second conduit system and which is selectively coupled to and driven by the expander, the compressor being effective to pressurize the air which is communicated to the fuel cell; and an electric machine which is operatively coupled to the expander and the compressor, the electric machine being effective to selectively convert torque generated by the expander into electrical power, and to selectively convert electrical power into mechanical torque for rotating the compressor.
According to a second aspect of the present invention, a method is provided for recovering potential energy stored within a pressurized gas used to power a fuel cell within a vehicle. The method includes the steps of: providing a first conduit system for transferring the pressurized gas to the fuel cell; providing an expander; operatively disposing the expander within the first conduit system; providing a motor/generator for producing electrical power from torque and for producing torque from electrical power; providing a second conduit system for transferring air to the fuel cell; providing a compressor; operatively disposing the compressor within second conduit system; operatively connecting the expander and the compressor to the motor/generator; selectively connecting the expander and the compressor; and channeling the pressurized gas through the expander, effective to rotatably drive the expander, thereby selectively driving the compressor and selectively causing the motor/generator to produce electrical power.
These and other features, aspects, and advantages of the invention will become apparent by reading the following specification and by reference to the following drawings.